Screw-cutting lathe



June 8, 1943. G. F. STXNSON SCREW-CUTTING LATHE Filed Aug. 20, 1941 2 Sheets-Sheet 1 E'e'derick Sir/M0221 M 9* June 8, 1943. F, STINSON SCREW-CUTTING LATHE Filed Aug. 20, 1941 2 Sheets-Sheet 2 frwenfor 63 0 e fiads'rzM 15 2mm Patented June 8, 1943 Application August 20, 1941, Serial No. 407,643 In Great Britain September 5, 1940 6 Claims.

When an ordinary screw-cutting lathe is to be used for cutting a multi-start thread, the usual practice is for one of the starts to be cut in the first instance and for the operator then to adjust the lathe back gears for the next start to be cut, and so on, an operation which not only takes time but also requires the services of a skilled operator for the correct setting of the gears.

, My main object is to provide a work-driving means, for use when a multi-start thread is to be cut, which will not only allow of saving time but can be operated by a relatively-unskilled operative of ordinary ability.

The invention broadly involves, for use with a screw-cutting lathe, adjustable work-driving means including co-axial members which are angularly adjustable and adapted to be held to one another in predetermined driving positions, the members being easily releasable for re-set ting purposes, the one adapted to be driven from the lathe spindle and the other adapted for driving the work. The members are provided with predetermined markings to facilitate re-setting.

In the accompanying sheets of drawings:

Figure 1 is a sectional elevation of one form of device according to the invention;

Figure 2 is an end view of the driven member, taken from the left of Figure 1;

Figure 3 is a developed peripheral view of the driving member and associated part of the driven member;

Figure 4 is a perspective view of the device, with the pin withdrawn, the work and workclamp being omitted in this view;

Figure 5 is a fragmentary sectional view of an alternative arrangement according to the invention;

Figure 6 is a sectional elevation of the device of Figures 1 to 4 provided with an attachment for cutting female threads, the section being on theline VI-VI of Figure 7;

Figure "I is a fragmentary end elevation of the attachment, taken from the right of Figure 6;

Figure 8 is a sectional elevation of another and very simple arrangement according to the invention, this view also showing part of the tail-stock of a screw-cutting centre lathe; and

Figure '9 is an end view of the driving member of Figure'8.

Like numerals are used as far as possible to denote similar parts throughout the different figures.

' In the constructionof Figures 1 to 4, for use with a screw-cutting centre lathe, the driving means includes a 'dri'vingmem'berl u in the form of a cup-shaped disc fast with a co-axial stem which is built up of two parts, II, I2, the former being adapted to be gripped in the chuck of the lathe (not shown). In the present instance the stem parts are formed with flanges I3 which are secured to the driving member I0 by screws I4. The driving member has an integral hub portion I5 on which is rotatively fitted the driven member I6, this carrying a bracket II secured by a screw I8. By means of the bracket H a work-clamp I9 can be driven in a manner known per se. The work-clamp is shown as having an arm 20 engaged in a slot in the bracket I'I, set screws ZI being provided in the bracket for looking the arm in the slot. By means of the set screw 22 the clamp I9 can be secured upon the work 23.

Extending from the centre of the driving member I0, through an opening in the driven member I6, is the other .part I2 of the stem, this being formed as a centre pin for supporting the work 23. This centre pin may if desired be slidingly disposed in the 'hub portion I5 of the driving member to abut against the end of a set screw (not shown) mounted co-axially of the stern part II, in a manner which will be well understood, whereby it can be axially positioned as desired.

It will be evident that, if desired, the driven member could be formed as a cup-shaped disc in the interior of which the driving member could be rotatively mounted.

Of the driving and driven members, one is provided with a plurality of angularly-spaced holes 25 and the other carries a pin 26 disposed to engage one or other of these holes according to the relative angular position of the two members, thus to provide a driving connection therebetween when they have been set. Corresponding to the positions of the holes are line markings 21 on the periphery of the disc member, to coact with a pointer marking on the other memher, and the holes are so positioned angularly from one another as to allow of the members being adjusted dependently upon the kind of multistart thread which is to be cut. The pin is provvided with a head to allow of it being manually withdrawn with ease when the members are to be re-set.

In the construction of Figures 1 to 4 the holes 25 are provided in the driven member I6, and the pin 26 is carried by the driving member It. The pin is shown as being fast with an operating It carries a lateral projection 29 3| secured by screws to the driving member, the cap having an undercut circular recess 32 communicating with the slot 30 and along which the projection can be moved, by twisting of the pin 26, to retain the latter in locking position. Figure 1 shows the pin in the position in which the projection 29 is at the bottom of the slot 30, i. e., in the recess 32. The pin in this position can be withdrawn (as shown by Figure 4) to allow of re-setting the members, or turned to carry the projection 29 partly round the recess 32, preferably until the handle 28 is in contact with the stem part II, to lock the members together.

In the construction of Figure 5 the pin 26 is not entirely withdrawable. The pin is pressed by a spring 33 in the engaging direction, the spring acting between the cap 3| and a circlip 34 on the pin.

Moreover, in the construction of Figure 5, the holes are provided in the driving member I0 and the pin 26 is carried by the driven member Hi.

In the present instance, of the holes 25 there are shown four (marked 35 in Figure 2) spaced at 90 from one another, and six (marked 35) spaced at 60 from one another. The line markings2'l are shown on the periphery of the disc l0. Associated with them are appropriate legends, such as the following, in this order: 360, 60, 90, 120, 180, 240, 270, and 300. The line markings 360, 90, 180 and 270 are of course co-related with the said four holes 35, and the line markings 360, 60, 120, 180, 240 and 300 with the said six h01es'36. Alternatively, the line markings may be associated with the following legends, in this order, 0, A, A A A; and Both such alternative legends are shown in Figure 3.

Thus, when a twin-start thread is to be cut, for example, the pointer marking 31 on the bracket I! is aligned with the line marking 360 or 0, the pin 26 inserted fully, and the first start then cut on the work in the ordinary Way. Thereupon the pin is released and the driven member, along with the work, rotated relativelyto the driving member to bring a diametricallyopposite hole 25 into association with the pin, as will be indicated by the pointer marking 31 being aligned with the marking of or 180. This turns the work through 180 degrees relatively to the lathe spindle, and after the pin has been fully inserted the second start can be cut.

Obviously, by the use of holes 25 disposed as shown provision is made for selectively cutting a thread of two, three, four or six starts, which are the commonest ones to be required in practice. Obviously, too, the bracket I! could, if desired, be replaced by a disc having the peripheral line markings 21, the pointer marking 31 then being provided on the driving disc.

If some other multi-start thread should be required than those for which provision has been made, it will be evident that, in the casein which the holes 25 and the line markings 21 are on the same member, as shown in the construction of Figure 5, whether it be the driving or the driven member, the said member (i. e., whichever has the holes 25 formed in it) may be replaced in toto by one having the alternative arrangement of holes in it and the necessary line markings on it. I

In practice the cup-shaped member may be built up of a plate and a ring portion detachably secured thereto, as by screws.

Conveniently, the

other member is recessed, as shown at 39, to be slidingly engaged by a ring 4| detachably secured to the cup-shaped member by screws 42, the ring 4| serving for detachably retaining the other member in position.

When female threads are to be out, use may be made of a suitable attachment to be secured to the driven member IE of Figures 1 to 4, the centre pin [2, bracket I! and the work-clamp I9 then being omitted. Figures 6 and '7 show one form of such an attachment. In this the work 23 is a tube secured in a hole in a block 43 by means of a set screw 44. The block has oppositely-disposed ears 45 secured to pairs of brackets 46 on a plate 47 which is in turn secured to the driven member I 6 in any convenient manner, as by screws 48. The work is entirely supported in this Way from the driven member, and the tail-stock centre pin (not shown) is not required. In the case of a long piece of work the usual roller steadies may be used. The cutting tool, of course, enters the work from the open end thereof remote from the headstock. The pointer marking 31 is placed on the periphery of the plate 41.

In the simple arrangement of Figures 8 and 9 which is adapted, by way of example, only for a triple-start thread, the driving member ID is again in the form of a cup-shaped disc having a short stem part I2 providing a centre pin for the Work 23, and in this instance the holes 25 are in the form of similar notches in its open edge, the notches being, of course, spaced angularly from one another at The end of the arm 20 of the work-c1amp I 9 is accurately shaped to engage one or other of these notches. When the first start has been cut the work and workclamp are moved axially as a whole on release of the tail-stock centre pin, indicated at 49, by turningof the wheel 5|, and as soon as the arm 20 is clear of the previously-engaged notch 25 the work and Work-clamp are turned together through 120 for the arm 20 to engage the second notch, the tail-stock center pin 49 then being tightened. After the second start has been cut the same operations are carried out, the arm 20 then engaging the third notch, and the third start then cut. The visual markings are in this case provided by the arm and the notches, respectively. Obviously, if desired, peripheral line markings may also be applied to the driving member ill in alignment with the centres of the notches, this being particularly advisable if the driving member is provided with a plurality of notches disposed from one another at angular distances corresponding to those of the holes 25 in Figure 2-i, e., for selectively cutting a two, three, four or six start thread.

In a modification of the arrangement of Figures 8 and 9, instead of the Work and workclamp being withdrawn as'a whole, the'arm 20 is slidably mounted in the work-clamp for retracting purposesfor example, in the manner indicated in Figures 1 and 3, or in Figure 5.

What I claim as my invention and desire to secure by Letters Patent of the United States is:

1. For use with a screw-cutting lathe when a multi-s'tart thread is to be cut, adjustable work-driving means including a driving member adapted to be driven from a lathe spindle, said member having a shank adapted to be gripped in the chuck of a screw-cutting lathe, a driven member adapted for driving the work, one of said members being of disc form and the other member being coaxially and rotatably mounted with respect thereto, one of said members having in it a plurality of holes spaced angularly from one another in a predetermined manner and the other of said members carrying a retractable pin adapted to selectively be engaged with said holes, and said disc member having a plurality of visual markings thereon spaced angularly according to the spacing of said holes, and the other of said members having a pointer marking to coact with said visual markings.

2. For use with a screw-cutting lathe when a multi-start thread is to be cut, adjustable workdriving means including a driving member, adapted to be driven from a lathe spindle, said member having a shank adapted to be gripped in the chuck of the screw-cutting lathe, a driven member adapted for driving the work, said driving member and said driven member being coaxially and rotatively mounted with respect to one another, said driven member having in it a plurality of holes spaced angularly from one another in a predetermined manner and said driving member carrying a retractable pin adapted to selectively be engaged with said holes, said driving member and pin adapted whereby said pin may be retained in locking position until manually released, and said driving member having a plurality of visual markings thereon spaced an ularly according to the spacing of said holes, and said driven member having a pointer marking thereon to coact with said visual markings.

3. For use with a screw-cutting lathe when a multi-start thread is to be cut, adjustable Work-driving means including a driving member adapted to be driven from a lathe spindle, having a shank adapted to be gripped in the chuck of the screw-cutting lathe, a driven member adapted for driving the work, one of said members being of cup shape and the other member being rotatively mounted therein, said cupshaped member having in it a plurality of holes spaced angularly from one another in a predetermined manner and the other of said members carrying a. retractable pin adapted to selectively be engaged with said holes, and said cupshaped member having a plurality of visual markings thereon spaced angularly according to the spacing of said holes, and the other of said members having a, pointer marking to coact with said visual markings.

4. For use with a screw-cutting lathe when a multi-start thread is to be cut, adjustable work-driving means including a driving member adapted to be driven from a lathe spindle, said member having a shank adapted to be gripped in the chuck of a screw-cutting lathe, a driven member adapted for driving the work, said driving member and said driven member being coaxially and rotatively mounted with respect to one another, one of said members having in it eight holes, four of said holes being spaced angularly from one another by 90 and six of said holes being spaced angularly from one another by and the other of said members carrying a retractable pin adapted to selectively be engaged with said holes, the member having the holesin it having also a plurality of visual markings on its periphery spaced angularly according to the spacing of said holes, and the other of said members having a pointer marking thereon to coact with said visual markings, whereby the setting of said members for cutting a two-start, three-start, four-start or six-start thread, as required, will be facilitated.

5. For use with a screw-cutting center lathe when a multi-start thread is to be cut, adjustable wcrk-driving means including a driving member having a shank adapted to be held in and driven from a lathe spindle, a driven member adapted for driving the work, said driving member carrying a center pin for the work, said centre pin extending through an opening in the other of said members, one of said members being of cup shape and the other being rotatively mounted therein, said cup-shaped member having in its base portion a plurality of holes spaced angularly from one another in a predetermined manner and the other of said members carrying a retractable slidable pin adapted to selectively be engaged with said holes, and said cupshaped member having a. plurality of visual markings on its periphery spaced angularly ac.- cording to the spacing of said holes, and the other of said members having a pointer marking to coact with said visual markings.

- 6. For use with a screw-cutting lathe when a multi-start thread of two, three, four or six starts is to be cut, adjustable work-driving means including a driving member adapted to be driven from a lathe spindle, said member having a shank adapted to be gripped in the chuck of a screw-cutting lathe, a driven member adapted for driving the work, said members being coaxially and rotatively mounted with respect to one another, one of said members hav- 

